Auxiliary fuel tank systems for aircraft and methods for their manufacture and use

ABSTRACT

Auxiliary fuel tank systems for aircraft and methods for their manufacture and use. In one embodiment, an aircraft can include a fuselage, at least one engine, and a fuel system configured to distribute fuel to at least one of the engine and an aerial refueling manifold. The aircraft can further include an auxiliary fuel tank system operably coupled to the fuel system. The auxiliary fuel tank system can include a master tank assembly and at least one slave tank assembly. The master tank assembly can be removably installed in the fuselage, and can include a master tank body configured to hold fuel. The master tank body can be configured to pass through a door in the fuselage without disassembly. The slave tank assembly can be removably installed in the fuselage at least proximate to the master tank assembly, and can include a slave tank body configured to hold fuel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application relates to copending U.S. Patent Application Nos.[Attorney Docket Nos. 03004.8112US and 03004.8113US] entitled “AuxiliaryFuel Tank Systems for Aircraft and Methods for Their Manufacture andUse,” filed concurrently herewith and incorporated herein in theirentireties by reference.

TECHNICAL FIELD

The following disclosure relates generally to aircraft fuel tank systemsand, more particularly, to auxiliary fuel tank systems that can beinstalled in aircraft fuselages.

BACKGROUND

Commercial transport aircraft are typically designed to carry a givenload of passengers, cargo, or passengers and cargo over a given range.Occasionally, however, the need arises to increase the range of theaircraft to serve other routes. Increasing the range generally requiresincreasing the fuel capacity of the aircraft.

Another situation in which it may be necessary to increase the fuelcapacity of an aircraft occurs when the role of the aircraft changes.For example, some military aircraft may serve as aerial refuelingtankers at one point in time and cargo carriers at another. In therefueling tanker role, auxiliary fuel tanks can be installed in the body(i.e., the fuselage) to increase the amount of fuel that can beoff-loaded to other aircraft in flight. In the cargo carrier role, thebody tanks can be removed to increase cargo capacity. Whether auxiliaryfuel tanks are added to increase range or to increase fuel off-loadcapacity, they should be relatively easy to install and remove so thatthe aircraft can be quickly changed into the desired configuration.

One known type of auxiliary fuel tank system includes an auxiliary tankinstalled in a fuselage of an aircraft. The system uses pneumaticpressure to transfer fuel from the auxiliary tank to a center-wing tankof the aircraft. The source of the pneumatic pressure can be cabin air.Alternatively, a supplemental blower system can be used to deliverpneumatic pressure when the cabin air is not sufficient to transfer thefuel. This particular auxiliary fuel tank includes double-wallconstruction.

Another known type of auxiliary fuel tank system includes a group ofthree tanks linked together in a fuselage of an aircraft in a cascadingfill/empty arrangement. Like the system described above, this systemalso uses pneumatic pressure to transfer fuel from the auxiliary tanksto a center-wing tank of the aircraft. In this system, however, theseparate tanks are filled in sequence with the first tank overflowinginto the next and continuing until all the tanks are full. Fuel istransferred out of the tanks in reverse. That is, the last tank emptiesfirst and then the next tank until all of the tanks are empty. The firsttank in the group to fill is connected to the main fuel system of theaircraft. The last tank in the group to fill is connected to theaircraft vent system and the pressurization source.

A further known type of auxiliary fuel tank system includes a group ofthree tanks having individual fuel inlet, fuel outlet, and ventmanifolds. Each tank includes individual valves to control the inflowand outflow of fuel from the tank. In addition, a single electricmotor-driven fuel pump can be installed in each tank for transferringfuel out of the tank. Alternatively, pneumatic pressure from an aircraftbleed air system can be individually provided to each of the tanks forfuel transfer.

Yet another known type of auxiliary fuel tank system includes two ormore auxiliary tanks ganged together with slip-together, low-levelinterconnects that maintain a uniform fuel level across all the tanks.Fuel is added to the tanks via a main fueling manifold of the aircraft.Pneumatic pressure from an aircraft bleed air system is used to flowfuel from the auxiliary tanks into integral aircraft fuel tanks. Ventingof the auxiliary tanks is provided via existing aircraft fuel systemvents.

A further known type of auxiliary fuel tank system can be found onKC-135 series aircraft. This system uses a number of flexible bladdersthat are permanently laced into a lower section of the fuselagestructure. The bladders include low-level interconnects that allow fuelto migrate from one bladder to the next. An aircraft fueling manifoldprovides fuel to the bladders for filling. Motor-driven pumps are usedto move fuel out of the bladders and return it to the aircraft fuelsystem or to an aerial refueling system. In this system, the auxiliarytank structure (i.e., the bladder) is single-wall construction.

SUMMARY

The present invention is directed generally toward auxiliary fuel tanksystems for aircraft and methods for their manufacture and use. Anaircraft fuel tank body configured in accordance with one aspect of theinvention includes a first end wall having at least a first aperture anda second end wall positioned opposite to the first end wall and havingat least a second aperture. The first and second apertures can beconfigured to accommodate passage of a fuel manifold extending throughthe fuel tank body. In one embodiment, the first and second aperturesare axially aligned with each other.

In another aspect of the invention, the first end wall further includesa third aperture and the second end wall further includes a fourthaperture. The first and second apertures can be configured toaccommodate passage of a fuel outlet manifold extending through the fueltank body and configured to transfer fuel out of the fuel tank body. Thethird and fourth apertures can be configured to accommodate passage of afuel inlet manifold extending through the fuel tank body and configuredto flow fuel into the fuel tank body.

In a further aspect of the invention, a modular fuel tank assembly foruse with an aircraft can include a first tank body and a first manifoldportion positioned at least partially in the first tank body. The firsttank body can include a first end wall and an opposite second end wall.The modular fuel tank assembly can further include a first manifoldinterconnect and a second manifold interconnect. The first manifoldinterconnect can be operably coupled to the first manifold portion andpositioned toward the first end wall of the first tank body. Similarly,the second manifold interconnect can be operably coupled to the firstmanifold portion and positioned toward the second end wall of the firsttank body. The first manifold interconnect can be configured to operablyconnect the first manifold portion to a second manifold portionassociated with a second tank body. Similarly, the second manifoldinterconnect can be configured to operably connect the first manifoldportion to a third manifold portion associated with a third tank body.

In yet another aspect of the invention, a method for increasing the fuelcapacity of an aircraft can include manufacturing a master tank assemblyand a slave tank assembly. Manufacturing a master tank assembly caninclude installing a first portion of a manifold in a first tank body.Manufacturing a slave tank assembly can include installing a secondportion of the manifold in a second tank body. The method can furtherinclude passing the master tank assembly through a door in a fuselage ofthe aircraft and operably coupling the first portion of the manifold toan aircraft fuel system. The method can additionally include passing theslave tank assembly through the door in the fuselage and operablycoupling the second portion of the manifold in the slave tank assemblyto the first portion of the manifold in the master tank assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially schematic, top isometric view of an aircraft withan auxiliary fuel tank system configured in accordance with anembodiment of the invention.

FIG. 2 is an enlarged isometric view of a forward tank group of theauxiliary fuel tank system of FIG. 1 configured in accordance with anembodiment of the invention.

FIG. 3 is an enlarged isometric view of an aft tank group of theauxiliary fuel tank system of FIG. 1 configured in accordance with anembodiment of the invention.

FIG. 4 is an enlarged isometric view of a tank body configured inaccordance with an embodiment of the invention.

FIG. 5 is an enlarged isometric view of a tank body configured inaccordance with another embodiment of the invention.

FIG. 6 is an enlarged isometric view of a master tank assembly of FIG. 3illustrating features of a fuel outlet manifold configured in accordancewith an embodiment of the invention.

FIGS. 7A-7B are enlarged, partially hidden side elevation views of ashut-off valve assembly of the fuel outlet manifold of FIG. 6,configured in accordance with an embodiment of the invention.

FIG. 8 is an enlarged isometric view of the master tank assembly of FIG.3 illustrating features of a fuel inlet manifold configured inaccordance with an embodiment of the invention.

FIG. 9 is an enlarged isometric view of the master tank assembly of FIG.3 illustrating features of a vent manifold configured in accordance withan embodiment of the invention.

FIG. 10 is an enlarged isometric view of the master tank assembly ofFIG. 3 illustrating features of a fuel gauging system configured inaccordance with an embodiment of the invention.

FIGS. 11A-11E are schematic diagrams illustrating modular features ofthe present invention that enable multiple tank configurations to beassembled from a common set of components in accordance with anembodiment of the invention.

DETAILED DESCRIPTION

The following disclosure describes auxiliary fuel tank systems foraircraft and methods for their manufacture and use. Certain details areset forth in the following description and in FIGS. 1-11E to provide athorough understanding of various embodiments of the invention. Otherdetails describing well-known structures and systems often associatedwith aircraft and auxiliary fuel tank systems are not set forth in thefollowing disclosure to avoid unnecessarily obscuring the description ofthe various embodiments of the invention.

Many of the details, dimensions, angles, and other features shown in theFigures are merely illustrative of particular embodiments of theinvention. Accordingly, other embodiments can have other details,dimensions, angles, and features without departing from the spirit orscope of the present invention. In addition, further embodiments of theinvention may be practiced without several of the details describedbelow.

In the Figures, identical reference numbers identify identical or atleast generally similar elements. To facilitate the discussion of anyparticular element, the most significant digit or digits of anyreference number refer to the Figure in which that element is firstintroduced. For example, element 110 is first introduced and discussedwith reference to FIG. 1.

FIG. 1 is a partially schematic, top isometric view of an aircraft 100having an auxiliary fuel tank system 110 configured in accordance withan embodiment of the invention. The aircraft 100 can include a fuselage102, a wing 104 extending outwardly from the fuselage 102, and engines105 (identified individually as a first engine 105 a and a second engine105 b) attached to the wing 104 to provide propulsive thrust to theaircraft 100. The fuselage 102 can include a forward cargo compartment106 having a forward cargo door 107 a and an aft cargo compartment 108having an aft cargo door 107 b. In one aspect of this embodiment, theauxiliary fuel tank system 110 includes a forward fuel tank group 112positioned in the forward cargo compartment 106 and an aft fuel tankgroup 114 positioned in the aft cargo compartment 108.

As described in greater detail below, both the forward and aft tankgroups 112 and 114 can be operably coupled to an aircraft fuel system130, an aircraft vent system 132, and a fuel management system (FMS) 134(all shown schematically in FIG. 1). The FMS 134 can receive statusinformation from the auxiliary fuel tank system 110 and transmit thisinformation to a flight controller or a display in the cockpit of theaircraft 100. This information can include, for example, the combinedtotal amount of fuel remaining in all of auxiliary tanks and theindividual amounts of fuel remaining in each of the tanks. In addition,as further described in greater detail below, the FMS 134 can alsocontrol and monitor auxiliary fuel tank inlet and outlet systems (notshown). The aircraft vent system 132 can maintain the pressure in theauxiliary fuel tank system 110 within an acceptable operating range. Theaircraft fuel system 130 can distribute fuel to the auxiliary fuel tanksystem 110 for filling of the forward tank group 112 and the aft tankgroup 114 during preflight procedures. In flight, the aircraft fuelsystem 130 can distribute fuel from the forward tank group 112 and theaft tank group 114 to the engines 105. In addition, the aircraft fuelsystem 130 can also distribute fuel from the forward tank group 112 andthe aft tank group 114 to an aerial refueling system (not shown) if theaircraft 100 includes such a refueling system. Alternatively, theaircraft fuel system 130 can distribute fuel from the aerial refuelingsystem to the forward tank group 112 and the aft tank group 114 ifdesired.

In another aspect of this embodiment, the forward tank group 112includes a first master tank assembly 120 a and a first end tankassembly 122 a. The aft tank group 114 can include a second master tankassembly 120 b, a mid tank assembly 121, and a second end tank assembly122 b. In the illustrated embodiment, the mid tank assembly 121 and theend tank assemblies 122 are all “slave” tank assemblies. As described ingreater detail below, these tanks are slave tanks because they arefilled and drained via equipment positioned in the corresponding“master” tanks 120.

In a further aspect of this embodiment, each of the tank assemblies 120,121, and 122 is shaped and sized to individually fit through the cargodoors 107 without substantial disassembly. For example, referring to theforward tank group 112, the first master tank assembly 120 a isconfigured to pass through the forward cargo door 107 a and be removablypositioned proximate to an aft bulkhead 103 a in the forward cargocompartment 106. Enough space is provided between the first master tankassembly 120 a and the bulkhead 103 a so that maintenance personnel canaccess the interfaces between the forward tank group 112 and theaircraft fuel system 130, the aircraft vent system 132, and the FMS 134.The first end tank assembly 122 a is also configured to pass through theforward cargo door 107 a, and is further configured to be operablycoupled to the first master tank assembly 120 a. Referring to the afttank group 114, the second master tank assembly 120 b is configured topass through the aft cargo door 107 b and be positioned proximate to aforward bulkhead 103 b in the aft cargo compartment 108. Like the firstmaster tank assembly 120 a, the second master tank assembly 120 b isspaced apart from the forward bulkhead 103 b so that maintenancepersonnel can access the interfaces between the aft tank group 114 andthe aircraft fuel system 130, the aircraft vent system 132, and the FMS134. The mid tank assembly 121 and the second end tank assembly 122 bare also configured to pass through the aft cargo door 107 b, and theyare further configured to be operably coupled to the second master tankassembly 120 b in series.

The number and arrangement of auxiliary fuel tanks positioned in eitherthe forward cargo compartment 106 or the aft cargo compartment 108 canbe varied to meet particular range and/or fuel off-load requirements.For example, two auxiliary fuel tanks can be positioned in the forwardcargo compartment 106 as illustrated in FIG. 1 by first moving the firstmaster tank assembly 120 a through the first cargo door 107 a, and thenpositioning the first master tank 120 a proximate to the aft bulkhead103 a. Next, the first end tank assembly 122 a can be moved through theforward cargo door 107 a and operably coupled to the first master tankassembly 120 a. Alternatively, if three auxiliary fuel tanks are neededin the forward cargo compartment 106, then the first end tank assembly122 a can be moved forward in the forward cargo compartment 106 to clearpassage for a mid tank assembly (such as the mid tank assembly 121)entering the forward cargo compartment 106 through the forward cargodoor 107 a. Once the mid tank assembly is in the forward cargocompartment 106, the three auxiliary fuel tanks in the forward cargocompartment 106 can be arranged in series similar to the aft tank group114. Similar staging sequences can be used to increase or decrease thenumber of auxiliary fuel tanks installed in either the forward cargocompartment 106 or the aft cargo compartment 108.

In the illustrated embodiment, both the forward tank group 112 and theaft tank group 114 are positioned outside a five-degree rotor burst cone(not shown) of the engines 105 in compliance with applicable regulatorystandards. However, the first master tank assembly 120 a can bepositioned within a broader 15-degree engine rotor burst cone (also notshown). Accordingly, in one aspect of this embodiment, the forward cargocompartment 106 can include shielding if necessary to adequately protectthe first master tank assembly 120 a from a rotor burst. In addition oras an alternative, the first master tank assembly 120 a can includereinforced tank walls to prevent a rupture in the event of a rotorburst. In another embodiment, the proximity of the second master tankassembly 120 b to a landing gear system (not shown) of the aircraft 100may make it susceptible to damage in the event of a landing gearcollapse. In such an embodiment, the second master tank assembly 120 bcan be made smaller than the corresponding slave tank assemblies 121 and122 to prevent damage to the second master tank assembly 120 b in theevent of a landing gear collapse.

The auxiliary fuel tank system 110 illustrated in FIG. 1 represents butone possible auxiliary fuel tank arrangement within the scope of thepresent disclosure. Accordingly, in other embodiments, other numbers offuel tanks in other arrangements can be used. For example, in one otherembodiment, the forward tank group 112 can include only the first mastertank assembly 120 a and/or the aft tank group 114 can include only thesecond master tank assembly 120 b. In another embodiment, one or more ofthe master tank assemblies 120 can be the outermost tanks in therespective tank groups, rather than the inner-most as illustrated inFIG. 1. In a further embodiment, the forward tank group 112 can bepositioned forward in the forward cargo compartment 106 rather than aft,and/or the aft tank group 114 can be positioned aft in the aft cargocompartment 108 rather than forward.

FIG. 2 is an enlarged isometric view of the forward tank group 112configured in accordance with an embodiment of the invention. In oneaspect of this embodiment, the first master tank assembly 120 a (“themaster tank assembly 120 a”) includes a first tank body 225 a, and thefirst end tank assembly 122 a (“the end tank assembly 122 a”) includes asecond tank body 225 b. The tank bodies 225 are the fuel-carryingportions of the corresponding tank assemblies 120 and 122, and are shownin phantom line in FIG. 2 for purposes of clarity. In one embodiment,the first tank body 225 a and the second tank body 225 b can be at leastapproximately identical. That is, they can have the same basicstructural configuration. As explained in greater detail below,utilizing common tank structures in this manner can significantly reducemanufacturing and assembly costs associated with auxiliary fuel tanksystems.

In a further aspect of this embodiment, the forward tank group 112includes a fuel system interface 231 configured to be operably coupledto the aircraft fuel system 130 (FIG. 1). As described in greater detailbelow, the fuel system interface 231 serves as a dual purpose fuelinlet/outlet for the forward tank group 112. For example, fuel can flowinto the master tank assembly 120 a and the end tank assembly 122 a fromthe fuel system interface 231 via a fuel inlet manifold 240. The fuelinlet manifold 240 is configured so that both of the tank assemblies canbe filled at approximately the same time, i.e., at least approximatelysimultaneously. Conversely, fuel can flow out of the master tankassembly 120 a and the end tank assembly 122 a through the fuel systeminterface 231 via a fuel outlet manifold 230. The fuel outlet manifold230 is configured so that both of the tank assemblies can be drained atapproximately the same time, i.e., at least approximatelysimultaneously.

The fuel outlet manifold 230 extends into both the master tank assembly120 a and the end tank assembly 122 a, and is coupled together by afirst tank interconnect 232 a bridging the gap between the two fueltanks. Similarly, the fuel inlet manifold 240 extends into both themaster tank assembly 120 a and the end tank assembly 122 a, and iscoupled together by a second tank interconnect 232 b. The tankinterconnects 232 can provide sealed interfaces between adjacent fueltanks and corresponding sections of the fuel outlet manifold 230. In oneembodiment, they can have double-wall construction and can includetelescoping and gimbaling features that accommodate relativemisalignment or motion between the fuel tanks.

In yet another aspect of this embodiment, the forward tank group 112includes a vent system interface 251 configured to be operably connectedto the aircraft vent system 132 (FIG. 1). As described in greater detailbelow, the vent system interface 251 provides venting of the master tankassembly 120 a and the end tank assembly 122 a via a vent manifold 250.The vent manifold 250 extends into both the master tank assembly 120 aand the end tank assembly 122 a, and is coupled together by a third tankinterconnect 232 c.

In a further aspect of this embodiment, the forward tank group 112includes an FMS interface 261 configured to be operably coupled to theFMS 134 (FIG. 1). As described in greater detail below, the FMSinterface 261 can transmit various fuel tank status information from theforward tank group 112 to the FMS 134 for use by a pilot or a flightcomputer. Such information can include, for example, usable fuelremaining in the forward tank group 112 as measured by a fuel gaugingsystem 260.

FIG. 3 is an enlarged isometric view of the aft tank group 114configured in accordance with an embodiment of the invention. In oneaspect of this embodiment, many portions of the aft tank group 114 areat least generally similar in structure and function to correspondingportions of the forward tank group 112 described above with reference toFIG. 2. For example, the second master tank assembly 120 b can be atleast generally similar in structure and function to the first mastertank assembly 120 a. Accordingly, the second master tank assembly 120 bcan include an aircraft fuel system interface 331, an aircraft ventsystem interface 351, and an FMS interface 361 that are at leastgenerally similar in structure and function to the correspondingportions of the first master tank assembly 120 a. Similarly, the secondend tank assembly 122 b (“the end tank assembly 122 b”) can be at leastgenerally similar in structure and function to the first end tankassembly 122 a. One clear difference between the forward tank group 112of FIG. 2 and the aft tank group 114, however, is the addition of themid tank assembly 121.

In a further aspect of this embodiment, many portions of the mid tankassembly 121 are at least generally similar in structure and function tocorresponding portions of the end tank assembly 122 b: One differencebetween these two tank assemblies, however, is that a number ofextensions can be added to the vent and fuel system manifolds in the midtank assembly 121 to extend the manifolds for coupling to the end tankassembly 122 b. For example, outlet manifold extensions 332 a can beadded to the fuel outlet manifold 230, and inlet manifold extensions 332b can be added to the fuel inlet manifold 240. Similarly, vent manifoldextensions 332 c can be added to the vent manifold 250. In addition tothe manifold extensions 332, additional tank interconnects 232 are alsorequired to operably couple the mid tank assembly 121 to the end tankassembly 122 b.

One feature of embodiments described above and illustrated in FIGS. 1-3is that both of the tanks in the forward tank group 112 (FIG. 1) can befilled and/or drained at least approximately simultaneously, and allthree of the tanks in the aft tank group 114 can be filled and/ordrained at least approximately simultaneously. One advantage of thisfeature over other tank systems that fill and drain in a cascadingmanner is that it can enable the auxiliary fuel tank system 110 (FIG. 1)to maintain a more consistent center of gravity location as the fueltanks are being filled and drained. Another advantage of this feature isthat it can enable the forward tank group 112 and the aft tank group 114to be filled and/or drained at a higher rate than comparably sized tanksthat fill and drain in a cascading manner.

FIG. 4 is an enlarged, isometric view of the tank body 225 configured inaccordance with an embodiment of the invention. In one aspect of thisembodiment, the tank body 225 is of double-wall construction andincludes an outer tank skin 442 and an inner tank skin 441. The innerskin 441 can act as a fuel-carrying membrane that can be configured tocarry at least about 250 gallons of fuel. For example, in one transportaircraft embodiment, the tank body 225 can be configured to carry atleast about 750 gallons of fuel. In another such embodiment, the tankbody 225 can be configured to carry at least about 1000 gallons of fuel.In other embodiments, the tank body 225 can be configured to carry moreor less fuel, depending on the particular needs of the aircraft and onany limiting physical dimensions of the aircraft. Such limiting physicaldimensions can include, for example, cargo compartment dimensions anddoor opening dimensions. The outer skin 442 can provide a redundant fuelbarrier to safeguard against leaks and protect the inner skin-441 fromexternal damage.

In another aspect of this embodiment, the tank body 225 includes a topaccess port 453 and a side access port 452. The top access port 453 caninclude an outer top door 454 a and an inner top door 454 b. The outertop door 454 a can removably cover a corresponding aperture in the outertank skin 442. The inner top door 454 b can be positioned directly belowthe outer top door 454 a, and can removably cover a correspondingaperture in the inner tank skin 441. Removal of the top doors 454 canprovide access to the interior of the tank body 225 for inspection ormaintenance of one or more of the systems installed within as describedin greater detail below.

The side access port 452 can include an outer side door 455 a and aninner side door 455 b. The outer side door 455 a can removably cover acorresponding aperture in the outer tank skin 442. Removal of the outerside door 455 a can provide access to a dry bay 458 extending betweenthe outer tank skin 442 and the inner tank skin 441. As described ingreater detail below, a number of fuel tank interface controls can behoused in the dry bay 458 so that they can be easily accessed bymaintenance personnel if needed when the tank body 225 is full of fuel.The inner side door 455 b can be positioned directly inboard of theouter side door 455 a, and can removably cover a corresponding aperturein the inner tank skin 441. Removal of the inner side door 455 b canprovide additional access to the interior of the tank body 225. In afurther aspect of this embodiment, the inner tank skin 441 forms a fuelsump 446 extending downwardly from the bottom of the tank body 225. Asfurther described in detail below, use of the fuel sump 446 helps toreduce the amount of fuel remaining in the tank body 225 after draining.

In yet another aspect of this embodiment, the tank body 225 includes afirst end wall 443 a and an opposite second end wall 443 b. In theillustrated embodiment, the end walls 443 have profiles that maximizethe available cross-sectional space in the aircraft cargo compartment.Accordingly, in this embodiment, the end walls 443 include beveledcorner portions 445 toward the bottom of the tank body 225 that followthe contour of the cargo compartment. As mentioned above, in otherembodiments, the tank body 225 can be made smaller and/or narrower toprevent damage during a landing gear collapse. In such embodiments, thebeveled corner portions 445 are not required and the end walls 443 canaccordingly be rectangular in shape.

In a further aspect of this embodiment, the first end wall 443 aincludes two fuel outlet apertures 432 a, two fuel inlet apertures 432b, and two vent apertures 432 c. These apertures are configured toaccommodate passage of the fuel outlet manifold 230, the fuel inletmanifold 240, and the vent manifold 250, respectively, described abovewith reference to FIGS. 2 and 3. The second end wall 443 b can includethe same complement of apertures described above for the first end wall443 a. In addition, however, the second end wall 432 b can furtherinclude a fuel system aperture 431, a vent system aperture 451, and anFMS aperture 461. As described above with reference to FIG. 2, theseapertures are configured to accommodate passage of correspondingaircraft interfaces (i.e., the fuel system interface 231, the ventsystem interface 251, and the FMS interface 261 shown in FIG. 2).

One feature of the embodiment described above and illustrated in FIG. 4is that the apertures 432 are common to both the first end wall 443 aand the second end wall 443 b. As described in greater detail below, oneadvantage of this feature is that a single tank body configuration(i.e., the tank body 225) can be used to construct the master tankassembly 120, the mid tank assembly 121, or the end tank assembly 122.If some of the end wall apertures are not used for a particular tankconfiguration, those apertures can be sealed with a suitable cover.

FIG. 5 is an enlarged isometric view of a tank body 525 configured inaccordance with another embodiment of the invention. Many aspects of thetank body 525 can be at least generally similar in structure andfunction to the tank body 225 describe above with reference to FIG. 4.In one particular aspect of this embodiment, however, the tank body 525includes a first end wall 543 a and an opposite second end wall 543 bthat are at least generally rectangular in shape and smaller than thecorresponding end walls 443 of the tank body 225. As described above, inone embodiment, the smaller tank body 525 can be used for a master orslave tank assembly when the tank assembly is installed in a positionthat could be susceptible to damage from landing gear collapse.

FIG. 6 is an enlarged isometric view of the second master tank assembly120 b (“the master tank assembly 120 b”) of FIG. 3 illustrating featuresof the fuel outlet manifold 230 configured in accordance with anembodiment of the invention. Selected internal components of the mastertank assembly 120 b, such as the fuel inlet manifold 240, the ventmanifold 250, and the fuel gauging system 260, have been omitted fromFIG. 6 for purposes of clarity. In one aspect of this embodiment, thefuel outlet manifold 230 includes a master tank portion 670 that isunique to the master tank assembly 120 b, a basic tank portion 660 thatis common to all master and slave tank assemblies, and an extensionportion 632 that interconnects the basic tank portion 660 to other basictank portions 660 positioned in adjacent tank assemblies.

In another aspect of this embodiment, the master tank portion 670 of thefuel outlet manifold 230 is operably coupled to a dual-purpose fuelinlet/outlet manifold 671. The fuel inlet/outlet manifold 671 includesthe aircraft fuel system interface 331, and bifurcates into a firstbranch 673 a and a corresponding second branch 673 b. Each branch 673 ofthe fuel inlet/outlet manifold 671 can include an inlet manifoldinterface 678 (identified individually as a first inlet manifoldinterface 678 a and a second inlet manifold interface 678 b). Asdescribed below in reference to FIG. 8, the inlet manifold interfaces678 are configured to be operably coupled to corresponding branches ofthe inlet manifold 240 (not shown).

In a further aspect of this embodiment, each branch 673 of the fuelinlet/outlet manifold 671 also includes an outlet manifold interface 679(identified individually as a first outlet manifold interface 679 a anda second outlet manifold interface 679 b). The first outlet manifoldinterface 679 a can be operably coupled to a corresponding first branch675 a of the master tank portion 670. Similarly, the second outletmanifold interface 679 b can be operably coupled to a correspondingsecond branch 675 b of the master tank portion 670. Each branch 675 ofthe master tank portion 670 can include a pump outlet check valve 676(identified individually as a first pump outlet check valve 676 a and asecond pump outlet check valve 676 b) operably coupled in series to afuel transfer pump 672 (identified individually as a first fuel transferpump 672 a and a second fuel transfer pump 672 b). Because they arepositioned within the inner tank volume of the master tank assembly 120b and exposed to fuel, the fuel transfer pumps 672 of the illustratedembodiment can be hydraulically driven. In other embodiments, such asembodiments in which the fuel transfer pumps 672 are positioned within adry bay 458 of the master tank assembly 120 b, the fuel transfer pumps672 can be electrically driven.

In yet another aspect of this embodiment, a pump pressure switch 674 isoperably coupled to each of the fuel transfer pumps 672 and isaccessibly mounted in the dry bay 458. The pump pressure switches 674can be operably connected to the FMS 134 (FIG. 1) through a control andmonitoring interface (not shown), and can provide a corresponding signalwhen the fuel transfer pumps 672 are operating. Placing the pumppressure switches 674 in an accessible portion of the dry bay 458enables them to be inspected or replaced without entering the interiorportion of the master tank assembly 120 b.

In a further aspect of this embodiment, the basic tank portion 660 ofthe fuel outlet manifold 230 includes a first fuel inlet duct 661 aoperably coupled to the first branch 675 a of the master tank portion670 and a second fuel inlet duct 661 b operably coupled to the secondbranch 675 b of the master tank portion 670. Each of the fuel inletducts 661 can include a corresponding fuel inlet 662 positioned at leastgenerally within the fuel sump 446. As described in greater detailbelow, in a further aspect of this embodiment, each fuel inlet 662 caninclude a corresponding shutoff valve assembly 664 configured to closethe corresponding fuel inlet 662 before the fuel inlet 662 loses prime,that is, before the fuel level in the tank falls below the fuel inlet662. Closing the fuel inlet 662 while it is still submerged in fuel canprevent the fuel outlet manifold 230 from ingesting air. This canminimize loss of pump prime when any one of two or more tanks in a tankgroup empties before one or more of the other tanks in the group.Accordingly, when fuel is no longer available in one of the tanks, thecorresponding fuel inlets 662 close to isolate the tank from the othersin the group.

In a further aspect of this embodiment, the extension portion 632 of thefuel outlet manifold 230 includes two outlet manifold extensions 332 a.Each of the outlet manifold extensions 332 a can be operably coupled toa corresponding one of the fuel inlet ducts 661. As described above withreference to FIG. 3, the outlet manifold extensions 332 a can extend thefuel outlet manifold 230 into an adjacent fuel tank assembly, such asthe mid tank assembly 121 or an end tank assembly 122 (FIGS. 2 and 3).

When fuel is being flowed into the master tank assembly 120 b throughthe fuel system interface 331, the pump outlet check valves 676 on theoutlet manifold 230 are closed causing the fuel to flow into the inletmanifold 240 (FIGS. 2 and 3) via the inlet manifold interfaces 678.Conversely, when it is desired to draw fuel from the master tankassembly 120 b, the pump outlet check valves 676 are opened and the fueltransfer pumps 672 pump fuel out of the master tank assembly 120 b viathe fuel inlet ducts 661. Concurrently, the fuel transfer pumps 672 arealso pumping fuel out of any adjoining tanks (e.g., the mid tankassembly 121 and the end tank assembly 122 of FIG. 3) via the outletmanifold-extensions 332 a. As fuel is being pumped out of the mastertank assembly 120 b through the fuel inlet/outlet manifold 671, shutoffvalves on the fuel inlet manifold 240 (not shown) are accordingly closedto prevent the fuel from back-flowing into the tanks via the inletmanifold 240.

FIGS. 7A-7B are enlarged, partially hidden side elevation views of theshutoff valve assembly 664 of FIG. 6 configured in accordance with anembodiment of the invention. Referring first to FIG. 7A, in one aspectof this embodiment, the shutoff valve assembly 664 includes a float 763operably coupled to a valve 765 via a linkage 766. The valve 765 can bepositioned inside the fuel inlet duct 661, and can be a butterfly typeconfigured to rotate about a shaft 767 as the position of the float 763changes. When fuel in the tank is at or above a first fuel level 731,the float 763 maintains the valve 765 in a fully open position as shownin FIG. 7A.

Referring next to FIG. 7B, as the fuel level drops from the first fuellevel 731 toward a second fuel level 732, the float 763 moves downwardlycausing the valve 765 to begin rotating about the shaft 767 toward aclosed position. When the fuel level reaches the second fuel level 732,the valve 765 is at least approximately fully closed as shown in FIG.7B. At this point, the fuel inlet 662 is still submerged, therebypreventing the fuel inlet duct 661 from ingesting air or other gaseoussubstances occupying the space in the fuel tank above the fuel. Even ifthe fuel level drops to a third fuel level 733, the fuel inlet 662 willstill be submerged. Accordingly, the distance between the second fuellevel 732 and the third fuel level 733 corresponds to a buffer between aclosed valve position and an uncovered inlet position. In a furtheraspect of this embodiment, by positioning the fuel inlet 662 and thecorresponding shutoff valve assembly 664 in the fuel sump 446, theamount of fuel remaining in the tank after draining is minimized.

The shutoff valve assembly 664 is but one type of mechanical shutoffvalve that can be used with the fuel outlet manifold 230 to avoid losingprime on one or more of the fuel transfer pumps 672. In otherembodiments, other types of shutoff valves can be used. For example, inone other embodiment, an electrically actuated valve can be used. In afurther embodiment, a hydraulically actuated valve can be used. In stillfurther embodiments, the shutoff valve assembly 664 can be omitted and,instead, a fuel level sensor can be used to command a valve, such as anelectrically actuated valve, to close the corresponding fuel inletbefore the fuel level drops below the inlet.

FIG. 8 is an enlarged isometric view of the master tank assembly 120 bof FIG. 3 illustrating features of the fuel inlet manifold 240configured in accordance with an embodiment of the invention. Selectedinternal components of the master tank assembly 120 b, such as the ventmanifold 250 and the fuel gauging system 260, have been omitted fromFIG. 8 for purposes of clarity. In addition, the fuel outlet manifold230 of FIG. 6 (which is normally coupled to the fuel inlet/outletmanifold 671 at the outlet manifold interfaces 679) is also not shown inFIG. 8 for purposes of clarity. In one aspect of this embodiment, thefuel inlet manifold 240 includes a master tank portion 870 that isunique to the master tank assembly 120 b, a basic tank portion 860 thatis common to all master and slave tank assemblies, and an extensionportion 832 that interconnects the basic tank portion 860 to other basictank portions 860 positioned in adjoining tank assemblies.

In another aspect of this embodiment, the master tank portion 870 of thefuel inlet manifold 240 includes a first branch 873 a operably coupledto the fuel inlet/outlet manifold 671 at the first inlet manifoldinterface 678 a and a second branch 873 b operably coupled to the fuelinlet/outlet manifold 671 at the second inlet manifold interface 678 b.Each branch 873 of the master tank portion 870 can include a primaryfueling valve 872 (identified individually as a first primary fuelingvalve 872 a and a second primary fueling valve 872 b) operably coupledin series to a secondary fueling valve 874 (identified individually as afirst secondary fueling valve 874 a and a second secondary fueling valve874 b). In addition, each branch 873 of the fuel inlet manifold 240 canalso include a refuel shutoff pressure switch 891 and a ground fuelingsolenoid valve 892 positioned in the dry bay 458. The refuel shutoffpressure switch 891 and the ground fueling solenoid valve 892 can beoperably coupled between the secondary fueling valve 874 and acorresponding pilot float valve 894. The pilot float valve 894 isconfigured to command the secondary fueling valve 874 closed when thefuel in the tank rises above the pilot float valve 894, thereby stoppingthe flow of fuel into the master tank assembly 120 b. If desired, theground fueling solenoid valve 892 can be used to override the pilotfloat valve 894 and increase the fuel level in the master tank assembly120 b above that normally allowed by the pilot fuel valve 894. Therefuel shutoff pressure switch 891 can be configured to send a signal tothe FMS 134 (FIG. 1) corresponding to the position of the secondaryfueling valve 874, that is, corresponding to whether the secondaryfueling valve 874 is open or closed.

In a further aspect of this embodiment, the master tank portion 870 ofthe fuel inlet manifold 240 can also include a solenoid pre-check valve896 positioned within the dry bay 458. The solenoid pre-check valve 896can be operably coupled to both of the pilot float valves 894. Thesolenoid pre-check valve 896 can provide a means for verifying that thepilot float valves 894 are functioning properly. For example, in oneembodiment, the solenoid pre-check valves 896 can be commanded throughthe FMS 134 (FIG. 1) to rapidly fill the pilot float valves 894 withfuel to verify that they cause the secondary fueling valves 874 to closeproperly. The FMS 134 can control the primary fueling valves 872, thesolenoid pre-check valves 896, the ground fueling solenoid valves 892,and the shutoff pressure switch 891 through the FMS interface 261described above with reference to FIG. 2.

In yet another aspect of this embodiment, the basic tank portion 860 ofthe fuel inlet manifold 240 includes a first fuel outlet duct 861 aoperably coupled to the first branch 873 a of the master tank portion870 and a second fuel outlet duct 861 b operably coupled to the secondbranch 873 b of the master tank portion 870. In the illustratedembodiment, each of the fuel outlet ducts 861 includes a piccolo tube862 (identified individually as a first piccolo tube 862 a and a secondpiccolo tube 862 b) having a plurality of fuel outlets 863. The fueloutlets 863 distribute incoming fuel into the interior of the mastertank assembly 120 b.

In a further aspect of this embodiment, the extension portion 832 of thefuel inlet manifold 240 includes two inlet manifold extensions 332 b.Each of the inlet manifold extensions 332 b can be operably coupled to acorresponding one of the fuel outlet ducts 861. As described above withreference to FIG. 3, the inlet manifold extensions 332 b can extend thefuel inlet manifold 240 into an adjoining fuel tank assembly, such asthe mid tank assembly 121 or an end tank assembly 122 (FIGS. 2 and 3).

To fill the master tank 120 b and any corresponding slave tanks (notshown) with fuel, the primary and secondary fueling valves 872 and 874are opened and fuel is introduced into the fuel inlet/outlet manifold671 via the fuel system interface 331. From the inlet/outlet manifold671, the fuel flows past the opened primary fueling valves 872 and theopened secondary fueling valves 874 to the fuel outlet ducts 861. Fromthere, the fuel flows into the master tank assembly 120 b from thecorresponding piccolo tubes 862. Concurrently, the fuel also flows toany adjoining tanks (e.g., the mid tank assembly 121 and the end tankassembly 122 of FIG. 3) via the inlet manifold extensions 332 b. As fuelis being flowed into the master tank assembly 120 b through the fuelinlet/outlet manifold 671, the pump outlet check valves 676 (FIG. 6) onthe fuel outlet manifold 230 are accordingly closed to prevent the fuelfrom back-flowing into the fuel transfer pumps 672 (also FIG. 6).

FIG. 9 is an enlarged isometric view of the master tank assembly 120 bof FIG. 3 illustrating features of the vent manifold 250 configured inaccordance with an embodiment of the invention. Selected internalcomponents of the master tank assembly 120 b, such as the fuel inletmanifold 240, the fuel outlet manifold 230, and the fuel gauging system260 have been omitted from FIG. 9 for purposes of clarity. In one aspectof this embodiment, the vent manifold 250 includes a master tank portion970 that is unique to the master tank assembly 120 b, a basic tankportion 960 that is common to all master and slave tank assemblies, andan extension portion 932 that interconnects the basic tank portion 960to other basic tank portions 960 positioned in adjoining tankassemblies.

In another aspect of this embodiment, the master tank portion 970 of thevent manifold 250 includes a first branch 971 a and a second branch 971b extending outwardly from the vent system interface 251. The basic tankportion 960 of the vent manifold 250 can include a first vent duct 961 aoperably coupled to the first branch 971 a and a second vent duct 961 boperably coupled to the second branch 971 b. The extension portion 932of the vent manifold 250 can include two vent manifold extensions 332 c.Each of the vent manifold extensions 332 c can be operably coupled to acorresponding one of the vent ducts 961. As described above withreference to FIG. 3, the vent manifold extensions 332 c can extend thevent manifold 250 into an adjoining fuel tank assembly, such as the midtank assembly 121 or an end tank assembly 122 (FIGS. 2 and 3).

In a further aspect of this embodiment, each of the vent ducts 961includes a first vent port 962 a and a second vent port 962 b. In theillustrated embodiment, the first vent port 962 a remains open at alltimes, but the second vent port 962 b includes a vent float valve 964configured to close the second vent port 962 b if the fuel level risesabove the second vent port 962 b. The arrangement of the vent floatvalves 964 can minimize the amount of fuel flowing into the ventmanifold 250 as the fuel sloshes around in the master tank assembly 120b.

FIG. 10 is an enlarged isometric view of the master tank assembly 120 bof FIG. 3 illustrating features of the fuel gauging system 260configured in accordance with an embodiment of the invention. Selectedinternal components of the master tank assembly 120 b, such as the fuelinlet manifold 240, the fuel outlet manifold 230, and the vent manifold250 have been omitted from FIG. 10 for purposes of clarity. In oneaspect of this embodiment, the fuel gauging system 260 includes fourfuel probes or fuel gauges 1060 mounted toward respective corners of themaster tank assembly 120 b. The plurality of fuel gauges 1060 can beoperably connected to the FMS interface 261 to provide fuel volumeinformation to the aircraft FMS 134 (FIG. 1).

FIGS. 11A-11E are schematic diagrams illustrating modular features ofthe present invention that enable at least three different tankconfigurations to be assembled from the same basic set of components.Referring first to FIG. 11A, a tank assembly sequence in accordance withone embodiment of the invention can begin with the basic tank body 225described above with reference to FIG. 4. Basic tank systems 1160 can beadded to the tank body 225 to produce a basic tank assembly 1190. Thebasic tank systems 1160 can include the basic tank portion 660 of thefuel outlet manifold 230 (FIG. 6), the basic tank portion 860 of thefuel inlet manifold 240 (FIG. 8), the basic tank portion 960 of the ventmanifold 250 (FIG. 9), and the fuel gauging system 260 (FIG. 10).

The basic tank assembly 1190 of FIG. 11A can form the basis of a numberof different tank configurations. For example, referring to FIG. 11B, inone embodiment, manifold extension systems 1132 can be added to thebasic tank assembly 1190 to produce the end tank assembly 122 describedabove with reference to FIGS. 1-3. The manifold extension systems 1132can include the extension portion 632 of the fuel outlet manifold 230(FIG. 6), the extension portion 832 of the fuel inlet manifold 240 (FIG.8), and the extension portion 932 of the vent manifold 250 (FIG. 9).Referring next to FIG. 11C, in another embodiment, two sets of themanifold extension systems 1132 can be added to the basic tank assembly1190 to produce the mid tank assembly 121 described above with referenceto FIGS. 1 and 3.

Referring next to FIG. 11D, in a further embodiment, master tank systems1170 can be added to the basic tank assembly 1190 to produce a singlemaster tank assembly 1122. The master tank systems 1170 can include themaster tank portion 670 of the fuel outlet manifold 230 (FIG. 6), themaster tank portion 870 of the fuel inlet manifold 240 (FIG. 8), and themaster tank portion 970 of the vent manifold 250 (FIG. 9). In oneembodiment, the single master tank assembly 1122 can be a master tankassembly that is configured for individual use without any correspondingslave tank assemblies. Alternatively, referring to FIG. 11E, in yetanother embodiment, the manifold extension systems 1132 can be added tothe single master tank assembly 1122 to create the master tank assembly120 described above with reference to FIGS. 2-10.

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but that various modifications may be made without deviating from thespirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

1-22. (canceled)
 23. A modular fuel tank assembly for use with anaircraft, the modular fuel tank assembly comprising: a first tank bodyhaving a first end wall and an opposite second end wall; a firstmanifold portion extending at least partially through the first tankbody; a fuel system interface operably coupled to the first manifoldportion and positioned toward the first end wall; and a manifoldinterconnect operably coupled to the first manifold portion andpositioned toward the second end wall, wherein the manifold interconnectis configured to operably couple the first manifold portion to a secondmanifold portion associated with a second tank body, and wherein thefuel system interface is configured to operably coupled the first andsecond manifold portions to a fuel system of the aircraft.
 24. Themodular fuel tank assembly of claim 23 wherein the first end wall has atleast a first aperture and the second end wall has at least a secondaperture, and wherein the fuel system interface extends at leastpartially through the first aperture and the manifold interconnectextends at least partially through the second aperture.
 25. The modularfuel tank assembly of claim 23 wherein the manifold interconnect isconfigured to operably couple the first manifold portion to the secondmanifold portion when the second tank body is positioned at leastproximate to the first tank body in a fuselage of the aircraft.
 26. Themodular fuel tank assembly of claim 23 wherein the fuel system interfaceis a dual-purpose interface configured to selectively transfer fuel outof the first tank body or flow fuel into the first tank body.
 27. Themodular fuel tank assembly of claim 23, further comprising at least onefuel transfer pump positioned in the first tank body and operablycoupled to the first manifold portion and the fuel system interface. 28.The modular fuel tank assembly of claim 23 wherein the first manifoldportion is a fuel outlet manifold portion configured to transfer fuelout of the first tank body via the fuel system interface, and whereinthe modular fuel tank assembly further comprises a fuel inlet manifoldportion extending at least partially through the first tank body, thefuel inlet manifold portion configured to flow fuel into the first tankbody via the fuel system interface.
 29. The modular fuel tank assemblyof claim 23 wherein the first manifold portion is a fuel outlet manifoldportion having at least one fuel outlet duct configured to withdraw fuelfrom the first tank body, and wherein the modular fuel tank assemblyfurther comprises a fuel inlet manifold portion extending at leastpartially through the first tank body, the fuel inlet manifold portionhaving at least one fuel inlet duct configured to flow fuel into thefirst tank body.
 30. The modular fuel tank assembly of claim 23 whereinthe first manifold portion is a fuel outlet manifold portion having atleast one fuel outlet duct configured to withdraw fuel from the firsttank body, and wherein the modular fuel tank assembly further comprises:a fuel inlet manifold portion extending at least partially through thefirst tank body, the fuel inlet manifold portion being operably coupledto the fuel system interface and having at least one fuel inlet ductconfigured to flow fuel into the first tank body; and a vent manifoldportion extending at least partially through the first tank body; and avent system interface operably coupled to the vent manifold portion andpositioned toward the first end wall.
 31. A method for increasing thefuel capacity of an aircraft, the method comprising: manufacturing amaster tank assembly by installing a first portion of a manifold in afirst tank body; passing the master tank assembly through a door in afuselage of the aircraft; operably coupling the first portion of themanifold to an aircraft fuel system; manufacturing a slave tank assemblyby installing a second portion of the manifold in a second tank body;passing the slave tank assembly through the door in the fuselage; andoperably coupling the second portion of the manifold in the slave tankassembly to the first portion of the manifold in the master tankassembly.
 32. The method of claim 31, further comprising positioning theslave tank assembly at least proximate to the master tank assembly in acargo compartment of the aircraft.
 33. The method of claim 31 whereinthe manifold is a fuel manifold, and wherein the method furthercomprises operably coupling the first and second portions of the fuelmanifold to a fuel system of the aircraft.
 34. The method of claim 31wherein the manifold is a fuel outlet manifold configured to transferfuel out of the master and slave tank assemblies, wherein manufacturinga master tank assembly further includes installing a first portion of afuel inlet manifold in the first tank body, wherein manufacturing aslave tank assembly further includes installing a second portion of thefuel inlet manifold in the second tank body, and wherein the methodfurther comprises: operably coupling the first portion of the fuel inletmanifold to the aircraft fuel system; and operably coupling the secondportion of the fuel inlet manifold in the slave tank assembly to thefirst portion of the fuel inlet manifold in the master tank assembly,wherein the fuel inlet manifold is configured to flow fuel into themaster and slave tank assemblies from the aircraft fuel system.
 35. Amethod for manufacturing an auxiliary fuel tank system for an aircraft,the method comprising: installing a first manifold portion having afirst manifold configuration in a first tank body having a first tankbody configuration; installing a second manifold portion having a secondmanifold configuration in a second tank body having a second tank bodyconfiguration, wherein the second manifold configuration is at leastapproximately identical to the first manifold configuration, and whereinthe second tank body configuration is at least approximately identicalto the first tank body configuration; positioning the first tank body atleast proximate to the second tank body; and operably coupling the firstmanifold portion to the second manifold portion.
 36. The method of claim35, further comprising: installing a third manifold portion having athird manifold configuration in a third tank body having a third tankbody configuration, wherein the third manifold configuration is at leastapproximately identical to the first manifold configuration, and whereinthe third tank body configuration is at least approximately identical tothe first tank body configuration; positioning the third tank body atleast proximate to the second tank body; and operably coupling the thirdmanifold portion to the second manifold portion.
 37. The method of claim35 wherein the first and second manifold portions are fuel manifoldportions configured to convey fuel, and wherein the method furthercomprises: installing a first vent manifold portion having a first ventmanifold configuration in the first tank body; installing a second ventmanifold portion having a second vent manifold configuration in thesecond tank body, wherein the second vent manifold configuration is atleast approximately identical to the first vent manifold configuration;and operably coupling the first vent manifold portion to the second ventmanifold portion.
 38. The method of claim 35 wherein the first andsecond manifold portions are fuel outlet manifold portions configured totransfer fuel out of the respective tank bodies, and wherein the methodfurther comprises: installing a first fuel inlet manifold portion havinga first fuel inlet manifold configuration in the first tank body;installing a second fuel inlet manifold portion having a second fuelinlet manifold configuration in the second tank body, wherein the secondfuel inlet manifold configuration is at least approximately identical tothe first fuel inlet manifold configuration; and operably coupling thefirst fuel inlet manifold portion to the second fuel inlet manifoldportion, wherein the first and second fuel inlet manifold portions areconfigured to flow fuel into the respective tank bodies.